An engine control box, which controls an ignition system of an engine, a fuel system, or an electric system of a transmission and the like in a concentrated manner, is mounted on a motorcycle or an ATV (All Terrain Vehicle). The engine control box and the objects to be controlled at respective portions of the vehicle are electrically connected with each other by way of harnesses and couplers which are divided in accordance with respective systems also as disclosed in JP-A-2002-70610